Pause the game, then hold L1 + R1 and press Circle(2), Left, Triangle, Circle, X. If you entered the code correctly, the phrase "Enter Cheat" will appear. The following codes may now be enabled after L1 + R1 are released:

Invincibility

Enable the "Cheat mode" code, then press Square, L2, L1, Triangle(2), L2. If you entered the code correctly, the game will automatically resume. Repeat this code to disable its effect. This code must be re-enabled with each new level. Your health will still decrease, but you will not die when it reaches zero. Note: You can still kill yourself with your own bazooka or grenade explosions.

Infinite ammunition

Enable the "Cheat mode" code, then press L2, L1, Square, L2, L1, R1. If you entered the code correctly, the game will automatically resume. Repeat this code to disable its effect.

Full Adrenaline meter

Enable the "Cheat mode" code, then press L1, R2, R1, Up, Triangle, Circle. If you entered the code correctly, the game will automatically resume.

Kill nemesis

Enable the "Cheat mode" code, then press Down, L2, L1, R1, Up, Square. If you entered the code correctly, the game will automatically resume. The person you have to hunt down in various missions will be killed.

Pickup OSS Document

Enable the "Cheat mode" code, then press Up, X, R2, R1, Up, Square. If you entered the code correctly, the game will automatically resume. Repeat this code to disable its effect.

Disable shellshock

Enable the "Cheat mode" code, then press L2, R1, L2, L1, Triangle(2). If you entered the code correctly, the game will automatically resume. Repeat this code to disable its effect.

Disable HUD

Enable the "Cheat mode" code, then press Circle, Down, Circle, Up, Triangle, Circle. If you entered the code correctly, the game will automatically resume. Repeat this code to disable its effect.

Commit suicide

Enable the "Cheat mode" code, then press X, Triangle, Circle, Right, Triangle, Circle. If you entered the code correctly, the game will automatically resume. Note: This code only works in single player mode.

Medkits

Successfully complete a level to get one medkit for every person in your squad that did not get killed.

Revives

Finish a mission with all objectives completed to get a revive.

Using automatic weapons effectively

Once you have an automatic weapon (such as the Thompson, MP5 SMG, etc.), you can use up a lot of ammunition on just one target. Instead of holding down the trigger the entire time, fire short controlled bursts at your enemies. The first shot you fire out from your weapon after you wait a moment will be the most accurate. Try to kill your enemies in short bursts with all automatic weapon.

Using mounted machine guns effectively

There are mounted machine guns that you can use to shoot Nazis. This is not easy and is also risky because you are shooting from a fixed position and cannot duck or hide. To get around this problem, send your squad directly next to the machine gun. They will use it instead of you and effectively mow down any enemies that are near by.

Easy completion of Operation Chariot mission

In the beginning of the first level, charge up to the Nazis and shoot with your machine gun. A soldier will shoot at you from a crane; ignore him. Go to the far right to find the cap. If you still have ammunition, more Nazis will appear; shoot them quickly. You must return to the first part of the dock you came from to complete the level.

When you are on the last level of the first attacks and the Panzer comes through the wall, let it blow up the mini houses. When they are blown up, get the grenades in them. If you get enough of them, you can blow up the Panzer. Keep throwing the grenades; it takes awhile.

Final objective in Operation Virus House mission

After making your way up the stairs to the courtyard where Von Schrader is found, use Adrenaline mode and defeat him. Then, run out of the courtyard and go up the stairs that were previously barricaded. Proceed to take out the two guards, then run through the doors until you get to a large control panel overlooking the courtyard. Press X, and the last objective of "Eliminate Von Schrader and Disable the Dirty Bomb" will be completed and the mission will be over.

Von Schrader's journal in final mission

In the final mission, you will have to find Von Schrader's journal. It is not located in the bunker where Von Schrader is found. It is located in the trenches at the bottom of the steep hill with the tank on top of it that gets blown up by the planes. It is directly below one of the gun emplacements in those trenches.

Defeating the Nemesis Bosses

Before you get to the Nemesis Bosses, fill up your adrenaline meter. This can be easily done by performing head shots. Once your meter is full, save it until you get to the Boss. Once you see him, press Up. You will now have limited immortality and unlimited ammunition. If you have a sniper rifle, you can shoot the Boss in the head a few times. If you have a sub-machine gun such as a Thompson or an STG-44, you can run up to the Nemesis and just shoot him. Another way to inflict serious damage is to use a rocket launcher. Note: You will not have unlimited ammunition for this -- it is best to have a good back-up weapon. If you still have not killed the Boss and your meter is almost empty, take cover. Also, if there are enemies surrounding the Boss, which is true in most circumstances, eliminate them before you attack the Boss.

Defeating the Nemesis in final mission

You will start with an M1 Garand and a BAR rifle at the beginning of the level. Walk down the bunker you start at and choose the bazooka for the Garand. Take the BAR and save the bazooka ammunition for the Nemesis. By doing this, you can use three bazooka shots on him and defuse the bomb.